page_title: Geotechnical engineering
section_title: Deep foundations
hierarchical_section_title: Geotechnical engineering / Building foundations / Deep foundations
caption_attribution_description: Piledriving at the Maxwell Bridge (Imola Avenue) in en:Napa, California. Taken by Argyriou on 20 September 2005.
context_page_description: Geotechnical engineering, also known as geotechnics, is the application of scientific methods and engineering principles to the acquisition, interpretation, and use of knowledge of materials of the Earth's crust and earth materials for the solution of engineering problems and the design of engineering works. It is the applied science of predicting the behavior of the Earth, its various materials and processes towards making the Earth more suitable for human activities and development.
  Geotechnical engineering embraces the fields of soil mechanics and rock mechanics, and has applications in the fields of geology, geophysics, hydrology, and other related sciences. Geotechnics is practiced by both engineering geologists and geotechnical engineers.
context_section_description: Deep foundations are used for structures or heavy loads when shallow foundations cannot provide adequate capacity, due to size and structural limitations. They may also be used to transfer building loads past weak or compressible soil layers. While shallow foundations rely solely on the bearing capacity of the soil beneath them, deep foundations can rely on end bearing resistance, frictional resistance along their length, or both in developing the required capacity. Geotechnical engineers use specialized tools, such as the cone penetration test, to estimate the amount of skin and end bearing resistance available in the subsurface.
  There are many types of deep foundations including piles, drilled shafts, caissons, piers, and earth stabilized columns. Large buildings such as skyscrapers typically require deep foundations. For example, the Jin Mao Tower in China uses tubular steel piles about 1m (3.3  feet) driven to a depth of 83.5m (274  feet) to support its weight.
  In buildings that are constructed and found to undergo settlement, underpinning piles can be used to stabilize the existing building.
  There are three ways to place piles for a deep foundation.  They can be driven, drilled, or installed by the use of an auger.  Driven piles are extended to their necessary depths with the application of external energy in the same way a nail is hammered.  There are four typical hammers used to drive such piles:  drop hammers, diesel hammers, hydraulic hammers, and air hammers.  Drop hammers simply drop a heavy weight onto the pile to drive it, while diesel hammers use a single-cylinder diesel engine to force piles through the Earth.  Similarly, hydraulic and air hammers supply energy to piles through hydraulic and air forces.  The energy imparted from a hammerhead varies with the type of hammer chosen and can be as high as a million-foot pounds for large scale diesel hammers, a very common hammerhead used in practice.  Piles are made of a variety of material including steel, timber, and concrete.   Drilled piles are created by first drilling a hole to the appropriate depth, and filling it with concrete.  Drilled piles can typically carry more load than driven piles, simply due to a larger diameter pile.  The auger method of pile installation is similar to drilled pile installation, but concrete is pumped into the hole as the auger is being removed.
caption: Pile-driving for a bridge in Napa, California.
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot A20", "Image Orientation": "Horizontal (normal)", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2005:09:20 14:32:24", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "196", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "180", "Thumbnail YResolution": "180", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1524", "Thumbnail JPEGInterchangeFormatLength": "4946", "EXIF ExposureTime": "1/500", "EXIF FNumber": "8", "EXIF ExifVersion": "0210", "EXIF DateTimeOriginal": "2005:09:20 14:32:24", "EXIF DateTimeDigitized": "2005:09:20 14:32:24", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "287/32", "EXIF ApertureValue": "6", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "97349/32768", "EXIF SubjectDistance": "749/500", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "173/32", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1600", "EXIF ExifImageLength": "1200", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "1600", "Interoperability RelatedImageLength": "1200", "EXIF InteroperabilityOffset": "1328", "EXIF FocalPlaneXResolution": "800000/103", "EXIF FocalPlaneYResolution": "240000/31", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera"}